Gigabit Ethernet

1
Gigabit Ethernet

• Group 1
• Harsh Sopory
• Kaushik Narayanan
• Nafeez Bin Taher

2
Background Information

• An introduction to Gigabit Ethernet

3
What Is Ethernet?

• Most successful LAN technology
• Operates at the Data Link Layer (layer 2) of the
  OSI reference model
• Acts as an interface between the MAC layer and
  transceivers in Ethernet hardware (Physical
  layer)
• Uses contention based medium access protocol
  CSMA/CD

4
Gigabit Ethernet

• Builds on top of the Ethernet protocol
• Allows data transfer speeds of 1000 Mbps
• Provides reliable communication between
  applications of the Network and Transport layers

5
IEEE 802.3 Gigabit Ethernet Specifications

• 802.3z
• 1000BASE-CX (short-haul copper)
• 1000BASE-LX (long-wavelength optics)
• 1000BASE-SX (short-wavelength optics)

• 802.3ab
• 1000BASE-T (twisted pair)
• 1000BASE-LH (long-haul)

6
Benefits of Gigabit Ethernet

• Higher data transfer rates
• Builds on current Ethernet
• Familiar technology
• Minimal staff training

7
Project Proposal

• Our aim and immediate goals

8
Project Aim

• Main Issue High costs associated with installing
  Gigabit Ethernet technology
• A source of high cost Opto-electronic
  transceiver module
• Project Aim Design cheaper module

9
Immediate Goals

• Set up test bed for future use
• Test module on evaluation board to confirm
  Gigabit transfer rates
• Test module with Gigabit Ethernet card to confirm
  successful data transfer

10
Brief Description of Module

• Agilent HFBR 53D5
• Consists of transmitter and receiver sections
• Transmitter section consists of an 850 nm VCSEL
  in an Optical Sub Assembly (OSA)
• Receiver consists of a Si PIN diode mounted on
  the OSA with a transimpedance preamplifier IC
• Signal Detect circuitry provided

11
Design Steps and Considerations

• Our design approach

12
Design Steps

• Construct Evaluation Board
• Remove Transceiver from card
• Place components and Transceiver on Board
• Test Board
• Connect Board to Gigabit Card
• Test setup with another Gigabit Card

13
Agilent Schematic

• The evaluation board that Agilent provides for
  testing the module is schematically represented
  below

14
Georgia Tech Evaluation Board

• In order to reduce costs, a GA Tech evaluation
  board was used and is shown below

15
Circuit Schematic

• All parts from the Agilent design were not
  necessary and the circuit layout used is shown
  below

16
Primary Design Considerations

• Power Supply Filtering Circuit
• Transmission Lines and Terminations

17
Power Supply Filtering Circuit

• Agilent Board Circuit was included to keep both
  parts of the transceiver independent of their
  power supply considerations
• Our Board Eliminated the need for the circuit by
  having two separate power supplies for both parts
  of the module

18
Transmission Lines and Terminations

• Transmission lines were eliminated from our
  boards
• Care was taken to keep the length of the lines
  less than 1/10th the signal wavelength i.e. 6 cm
• Sharp angles on the board were avoided

19
Miscellaneous Considerations

• Reduce susceptibility to noise
• Accomplished by using differential inputs as
  opposed to single-ended ones
• Top and bottom of board unconnected
• Used vias to connect the two

20
Component Details

• Capacitors mainly used for Decoupling
• Capacitors used to separate power supplies from
  circuit.
• Protect circuits from transients
• Resistors used for terminations and biasing

21
Problems Faced

• Soldering
• surface mount components
• Top and Bottom of board unconnected
• Power not getting through from one side to
  another
• Solved by allowing solder to drip through to form
  a connection

22
Connecting Card to Board

• Used RG174 Cable with SMA connectors to connect
  card to board
• Removed resistor networks from Gigabit card
• Used wire to connect signal detect pin from board
  to card
• Connected the grounds of board and card with wire

23
Test Layout
Resistor networks removed
24
Results

• Eye diagrams and bit error rate data

25
Board Test Setup
Power
Ch1 Oscilloscope
Pattern Generator
RX
TX
Ch2 Oscilloscope
Pattern Generator
RX
TX
Fiber Optic Cable
26
Eye diagram for 10m Cable
27
Eye diagram for 100m Cable
28
Significance of Eye Diagram

• Eye formed by superimposition of pseudorandom bit
  patterns
• Eye generated met standard specifications
• Indicated signal quality was acceptable

Standard Eye Mask
Superimposed Eye Mask
29
Bit Error Rate Data

• 10m cable No errors encountered
• 100m cable No errors encountered
• Errors appeared when using PN23 encoding scheme
  at 1.2 Gbps
• Error rate 2.3 errors/Mb

30
Verification of results

• Card was plugged into computer
• Passed loop-back diagnostic test
• Connected to another computer using fiber optic
  cable
• Packets sent and received with no errors
• File transferred successfully over link

31
Computers on LAN
32
Summary

• The card was assembled and tested successfully
• Questions?
• Harsh Sopory (gte648h)
• Kaushik Narayanan (gte678h)
• Nafeez Bin Taher (gte078h)